


promise

by minthalo



Series: a/b/o miya twins [5]
Category: Haikyuu!!
Genre: Alpha Miya Osamu, Alpha Ojiro Aran, Alpha/Beta/Omega Dynamics, Alternate Universe, Angst, Angst with a Happy Ending, Beta Atsumu, Beta Suna Rintarou, Brotherly Angst, Brotherly Bonding, Brotherly Love, Family Angst, Family Bonding, M/M, Omega Verse, Omegaverse, no its not incest be normal, second years as third years
Language: English
Status: Completed
Published: 2021-02-12
Updated: 2021-02-12
Packaged: 2021-03-18 03:42:46
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,755
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28736682
Author URL: https://archiveofourown.org/users/minthalo/pseuds/minthalo
Summary: “You’re the fuckin’ worst, Atsumu. Glad I’m not goin’ pro with you, followin’ you around like a damn dog. I’m sick of bein’ your shadow.”Atsumu’s mouth snaps shut, going dead quiet. He stares at Osamu, the fire behind his eyes burnt out the moment those words left his brother’s mouth.Osamu regrets it immediately. This isn’t how he planned on telling him, this isn’t at all how he wanted to say he wasn’t following through with their plan, with Atsumu’s dream.“W-what?” Atsumu’s voice is quiet, somehow it hurts Osamu more than a punch to the throat.Osamu tells Atsumu he isn't playing volleyball after high school.
Relationships: Miya Atsumu & Miya Osamu, Miya Atsumu & Ojiro Aran, Miya Osamu/Suna Rintarou
Series: a/b/o miya twins [5]
Series URL: https://archiveofourown.org/series/2087349
Comments: 2
Kudos: 101





	promise

**Author's Note:**

> this whole au was created just so i could write this fight tbh
> 
> im not 100% happy with it, but it's been like. almost a month since ive written anything for this au and it's like. 2:30 am which we all know is prime fic writing time. 
> 
> enjoy!

It starts with a fight.

It’s been a long couple of weeks, the final volleyball season of their third year is coming to a close. The twins have been getting offers left and right from various colleges from around the country, Atsumu more than his brother. A few pro teams went so far to invite Atsumu to their practices. 

He doesn’t seem to even consider those offers.

It infuriates Osamu, not that his brother has caught onto it. Osamu’s been on edge around him for a while, snapping at him for the smallest of things. Atsumu doesn’t know why, but he refuses to back down when Osamu picks a fight with him.

It’s over something stupid, Osamu can’t remeber what triggered the argument. One moment they were standing next to each other in Atsumu’s bedroom, the next they were shouting insults. Low blows back and forth, Osamu picks at his low grades and piss colored hair. Atsumu insults his wardrobe and shitty serves at practice that day. 

“You’re the fuckin’ worst, Atsumu. Glad I’m not goin’ pro with you, followin’ you around like a damn dog. I’m sick of bein’ your shadow.”

Atsumu’s mouth snaps shut, going dead quiet. He stares at Osamu, the fire behind his eyes burnt out the moment those words left his brother’s mouth.

Osamu regrets it immediately. This isn’t how he planned on telling him, this isn’t at all how he wanted to say he wasn’t following through with their plan, with Atsumu’s dream. 

“W-what?” Atsumu’s voice is quiet, somehow it hurts Osamu more than a punch to the throat.

“‘Tsumu-”

“What the fuck do you mean you’re not goin’ pro?” His voice raises with each word, dripping with venom. “You’re quitting? What the fuck do you mean you’re quitting, ‘Samu?” 

Atsumu grabs the first thing he can get his hands on. A controller to the game system plugged into the television set on the floor. He chucks it, hard. Osamu reacts quickly, catching it before it hits his chest, it leaves his palms stinging, the joystick bending under his thumb.

Every sense of clarity and self control goes out the window, he’s back to being as pissed off as he was earlier, even more so now. He chucks it back, Atsumu dodges it, the controller hitting the wall. The backing pops off, Osamu might have broken it. He doesn’t know, he can’t bring himself to care.

“You’re such an asshole, ‘Samu! How dare you quit on me right now, this is our  _ dream,  _ this was our whole fuckin’ plan! We’ve been talkin’ about this since we were kids! We’re gonna make it to the olympics, you piece of shit! You’re gonna end it like this, quit before we even get the chance? Fuck you.”

Atsumu storms off, his chest bumping against Osamu’s shoulder on his way out. Osamu follows him out the front door, marching off in the opposite direction. 

Atsumu finds himself about a mile away from their home, a park a few blocks away from their high school. He’s beyond pissed off, he knows he’s being a bit irrational, but he can’t shake the anger he has towards his brother at the moment. 

Osamu is throwing away years of their lives, all the practices, the training, the teams they were on throughout their childhood, it was all a build up to this moment. Graduating high school and going pro, on their way to the olympic stage together. He’s jumping ship before they can have a real chance.

He stops by a large tree and sits down, there’s a bench off in the distance, but Atsumu can’t bring himself to walk anymore. He lays on his back and pulls his phone out. Usually in a moment like this, being so upset over something he’d vent to his brother. Osamu would call him a dramatic asshole, smack him upside the head, but he’d offer advice in the end.

He doesn’t know what to do when the problem is Osamu. Whenever they fight it’s a few hours of yelling, followed by a physical fight, but after that they’ve calmed down enough to fix the problem, or ignore it, whatever is easiest. They never apologize, they don’t have to.

This fight is different, this isn’t Atsumu being an asshole on the court, or stealing some of Osamu’s food. This isn’t Osamu hiding his notes before an exam on a subject he’s struggling in. This is Osamu changing his path on the future Atsumu always thought they’d take together.

He scrolls past a few different numbers in his contacts. He almost calls Sakusa, they talk more often now, but he wouldn’t understand. Both him and his cousin plan to go pro, they’ll be in this together, the way they always were.

He stops at Aran’s number. They haven’t talked outside of the old Inarizaki group chat in almost a month. He misses him really, Aran went off to college cities away in hopes to play pro. One of the things Atsumu is most excited about graduating is the chance to play with him again.

He presses call. 

It’s a moment of weakness, he knows this, and regrets it almost immediately after he clicks the contact, but before he can hang up Aran actually answers.

“Hello?”

Atsumu clamps a hand over his mouth to prevent Aran from hearing the embarrassing squeak that threatens to break out.

“Atsumu? I can hear you breathing. I know you’re there.”

Atsumu swallows and takes a breath, “hey, Aran.” He winces, his voice sounds small even to himself.

“You okay, ‘Tsumu?” Concern is clear in Aran’s voice, it’s comforting to know he still cares about him. 

Atsumu sits up, “yeah, ‘m fine. Sort of, not really. I need… I need advice.” He chews on his bottom lip.

“Oh, do you now?” Atsumu can hear the smirk in his old upperclassmen’s voice. “What could the great Miya Atsumu, captain of Inarizaki High’s famous volleyball team possibly need advice on.”

Atsumu lets out a light laugh, he actually misses being teased like this. “Ha ha, very funny.” 

“Seriously though, it’s pretty late for a spontaneous call like this. What’s up?”

Atsumu shifts, “yeah, I know it’s late, sorry.”

“It’s fine, ‘Tsumu. We haven’t talked in a while, it was nice to see your dumb photo pop up.”

Atsumu cracks a smile at that, he knows the photo well, it was taken his second year, a week after they lost to Karasuno. He was over doing it with serve practice again, Osamu attempted to drag him out of the gym but he refused to listen.

Kita caught him and dragged him out by his ear when he resisted. Suna snapped the photo and spread it around the school like wildfire. 

It’s a few seconds before he speaks again. “Osamu is quitting. He’s not goin’ pro with me.” 

“Ah.” Aran says, “so that’s what’s buggin’ you, huh?”

Atsumu nods, even though the other can’t see him. “Yeah. He just told me now, while we were arguin’.”

“You upset?

“Of course I’m upset!” Atsumu yells, “he’s throwing away everything we’ve worked so hard for! Years of training, and practice together! He’s got all these amazing offers from different schools, schools I’ve been invited to too! The idiot isn’t takin’ any of them! He’s abandoning it all, we could be great, we could go so far together and he’s quittin’ before we have a real chance to try!”

Aran listens to his little rant, by the time he’s done he’s panting, he’s screamed his heart out. Atsumu feels lost, abandoned. For the first time in his life he doesn’t have a clear picture of what his future holds.

“He’s leaving the sport, not you ‘Tsumu.”

“Same thing.” He winces hearing his voice crack. 

“Have you tried talking to him?”

“We did talk-“

“No, you argued. Not even properly I’m guessing. You most likely spat some insults at each other, then did something physical, and both stormed off. You’re the same really, anyone who thinks you’re the more dramatic one has never spent time with you two together.”

Atsumu lets out a weak laugh at that, “‘Samu’s just as bad as me, just quiet about it.”

Aran smiles softly, hearing Atsumu laugh, even soft like that, means he’s getting through to him. “Talk to him. Try and consider his side of all of this. Maybe he just lost the love for this sport, you don’t want to force him into a life he doesn’t want. Maybe this isn’t the big act of betrayal you think it is, you’re not the same, not two halves of one person. Maybe this is your brother becoming his own person.”

Atsumu shifts, crossing his legs. “We don’t… we don’t ever talk about this kind of stuff. It’s always been one plan, play volleyball, be the best at it. I never thought he’d change his mind.”

“Well, you have to start somewhere.”

“Yeah.” Atsumu takes a deep breath, he feels a bit better, like a weight has been taken off his chest. “Thank’s Aran. You’re the best. Savin’ my ass like you never left.”

Aran laughs, “anytime, ‘Tsumu. Believe it or not I miss your dumbass. You can call me anytime, you know? Preferably earlier than the middle of the night.”

Atsumu lets out a sheepish laugh, “yeah, sorry. I’m takin’ this as an invitation to text you more. Open up your camera roll, I have the best memes.”

“Oh no.”

“One of which made Omi-Omi facetime me directly after I sent it with a threat to drive to Hyogo himself to break my phone.“ Atsumu says proudly.

Aran laughs, “still talkin’ to him then, yeah?”

“Mmhm, and Komori sometimes, Kageyama too. He doesn’t text back often though. Karasuno has only gotten stronger by the way. It’s kinda scary to see what they can do.”

“They’re somethin’ else huh, but so are you. If you’re gonna send me awful memes at least send them to Kita too, don’t make me suffer alone. Go talk to your brother, text me after, or tomorrow mornin’ tell me how it goes.”

Atsumu stands up stretching out his back, letting out a satisfied sigh when it cracks just right. “I will, I promise.”

Osamu ends up outside of Suna’s house. It’s the middle of the night, he debates turning around and going somewhere else. It’s late, he doesn’t want to bother his boyfriend with something as stupid as a fight with his twin.

Even if this fight feels different. This isn’t anything like the ones they’ve had before, where they scream, and yell, hash it out physically. They can’t fix this by ignoring it, pretending nothing is wrong, they way they could with previous fights, as if their scuffle didn’t get them suspended from club activities for a week.

Before he can make the decision to turn back around the window above him opens, Suna leaning outside. He grins down at him, face falling the moment he sees the expression on his boyfriend’s face. 

He leans out the window, holding his arms out so Osamu can climb up the wall. They’ve gotten better at this, it’s familiar now. Being able to sneak into his boyfriend’s room almost silently after a year of doing this on an almost weekly basis. 

The landing is still rough, Osamu tumbles in, rolling and landing on his back. He shakes his head and sits up. Suna helps him to his feet, pulling him to his bed. 

They sit up on Suna’s bed for a few minutes, Osaumu pulls Suna’s legs over his own, dipping his head down to rest it on Suna’s shoulder. Suna has an arm around him, tracing small shapes into his shoulder. 

They stay like that for a while, in silence. Eventually Suna opens his mouth to ask what happened, why Osamu was outside his window in the middle of the night without any warning.

Osamu cuts him off before he can say anything. “I told him.” 

Suna’s shoulder’s drop, he knows exactly what happened.

“Yeah? How did he take it?”

“What do you think?” Osamu spits out, he pulls his head up, glaring at the wall next to the bed. 

“Hey,” Suna rubs his shoulders, so he isn’t so tense. “C’mon. Tell me exactly what happened.”

“We were fighting,” Osamu starts, he lifts one hand to rub his face, trying to recall all the details. “I don’t remember what started it, I don’t even know how school even got brought up. He’s just been so frustrating lately, I don’t know what it is.”

Suna nods, “you’ve been fighting more lately.” He comments quietly.

“He’s been fucking insuferable lately. He’s a selfish asshole, and I can’t stand him. Every time I’m around him it pisses me off, he’s a cocky asshole who never shuts up. That’s the reason I’m quitting, just so I don’t have to deal with his ass anymore. And he has the fuckin’ nerve to be pissed im not following him into college, I’m sick of it! I don’t wanna be around him anymore, I can’t wait until this year is over, so I can finally be rid of him.”

Osamu’s practically out of breath by the end of his rant. Suna smacks his forehead, harder than he intended, but enough to snap him out of whatever daze he’s in. 

“Ouch! Rin, what the hell?” Osamu tries to keep his voice down, Suna’s family is still asleep down the hall.

“You’re an idiot, you know that?” Suna puts a hand on his cheek, lifting his head so they make eye contact. “You’re just mad, you don’t mean any of this.”

Osamu narrows his eyes, “So what if I’m mad, that doesn’t change anything that happened.”

“You don’t hate Atsumu, you’re mad at him, and you’re allowed to be, but you don’t hate him. He’s your brother, your best friend, you love him. Okay, so he blew up on you after you told him you were quitting, did you stop to think about how he’s feeling right now?”

“Why the fuck should I do that?” Osamu snaps, “I’m not his damn babysitter. I won’t fuckin’ coddle him.”

“I’m not sayin’ you have to baby him.” Suna huffs, “Just think about how he’s feeling for a second. You’re his best friend ‘Samu, you’ve been by his side his whole life, and you basically told him you’re leaving him.”

“I’m not leavin’ him, I just don’t wanna play volleyball anymore.” 

“Yes, I know that, you know that, deep down he does too. But right now he’s not thinking clearly, you can relate to that.” Suna pinches his cheek lightly. 

Osamu pulls his head out of his hands, frowning. “I’m thinking just fine.”

“Yeah, okay. That’s why you stormed off after arguing.”

“He did too, left first actually.”

“Yeah, well he’s a dramatic asshole, but he’s not selfish. He has all these offers from different schools and you know which ones he’s been lookin’ at?”

Osamu swallows, turning his head to look at the wall. “The schools I got offers from.”

“This is something you’ve done together your whole lives, it’s not a mystery he blew up after you let him know you’re quitting. It’s no wonder you’ve been so tense lately, you’ve been sitting on this for years.”

Suna takes his hand, bringing it to his lips. He presses a soft kiss to his knuckles, lifting it to kiss the scent glands on his wrist. Osamu softens, Suna always knows what to say when he’s tense like this.

“It’s alright to be mad, you’re allowed to be. Atsumu isn’t handling this in the best way either. Neither of you are in the wrong, but neither of you are right either.”

Suna’s right, this could have been avoided if Osamu told him he wanted to quit when he first had the idea in their second year. It would have still ended in a fight, but nothing this severe, he wouldn’t have led his brother on with false hope for so long. There isn’t anything he can do about it now, he has to face the issue head on.

Suna presses a soft kiss to his temple, Osamu lifts his head up and catches his lips.

“Thank you.” He whispers.

“Hey, what’s a boyfriend for? Someone has to stop your meltdowns.” He teases lightly.

Osamu rolls his eyes, pulling him closer anyway. He nuzzles into his neck, rubbing his cheek against his scent gland.

“Is it bad I think I’ll miss you more than ‘Tsumu?” He asks quietly.

They haven’t talked much about it. Suna has already committed to a school hours away from their home. He’s playing pro, but never pressured Osamu to do the same. He’s known his heart isn’t in the sport anymore.

He lets out a soft laugh, pulling Osamu’s head out of his neck to brush their noses together. “Nah, just don’t tell him that.”

They lay like that for a bit longer, exchanging soft kisses between quiet banter. Eventually Osamu pushes Suna’s legs off his lap, slipping out of the bed. Suna offers to walk him back home, but Osamu declines. 

He presses one last kiss to Suna’s lips, whispering a quiet thank you against him before climbing back out the window.

He walks up to his house the same time Atsumu does, his brother coming from the opposite direction. The two of them stop, and stare at each other for a solid thirty seconds before one moves. Osamu cracks first, he steps closer to him, it looks like he’s about to walk past Atsumu when he grabs his arm instead, dragging him with him.

“H-hey, what the hell are you doing? Where are we going?”

They end up in their backyard, sitting on the two swings their father chained to a sturdy tree all those years ago.

They’re silent, facing the fence in their backyard, the two of them looking up at the sky. The stars are out, and the moon is bright. Every light in their house behind them is off, their entire family asleep.

“I’m not going to apologize for quitting.”

Atsumu turns in the swing, twisting the chain. He throws his legs onto Osamu’s seat, one on each side of his leg, forcing them to look at each other.

“I’m not mad that you’re quitting. I’m,” He sighs, rubbing his face, “I don’t know.” He says into the palm of his hand.

They sit in silence again, Atsumu pulls his hands back, fisting them in his lap. “I called Aran.”

“What?” Osamu straightens his back, genuinely shocked. “Seriously? He actually answered?”

He nods, “yeah, he did. I wanted some guidance or whatever.”

Osamu nods, tipping his head back. “Well what did he say?”

“That I wasn’t thinking of you, that I was being selfish, as usual-”

Osamu huffs, “He didn’t say that.”

“No, but he might as well have. I didn’t think of you.”

“I didn’t think of you either. I should have told you earlier, or waited until we weren’t arguing.” He pauses, taking a deep breath, “I don’t feel the same as you, not anymore. I did at one point, I cared more about volleyball than anything. I haven’t, not for a while. Not since before you left for that training camp a year ago.”

Atsumu frowns, he should have noticed. He’s been so focused on himself he didn’t notice his brother has drifted so far away from the future he always thought they’d have together.

“I didn’t notice, I should have. I always thought we’d be in this together, Miya twins take the volleyball world by storm. I didn’t realize you didn’t want that anymore, I shouldn’t have blamed you, it’s not your fault. I wanted to do this together, but I won’t force you into a future you don’t want, that’s not right.” 

“You’re still gonna take the world by storm, I know it.” Osamu says firmly.

“Without you.” Atsumu flinches after he says it, “I… I just thought we’d always be together.”

Osamu hums, he let go of that a long time ago, not realizing his brother still held to it so tightly. They’re not the same person, they never were. 

“You’re not selfish ya know.” Osamu says after a moment of silence, “you were gonna turn down scholarships to powerhouse schools because I wasn’t invited. That’s not selfish. Don’t think that low of yourself, asshole.”

“Yeah, yeah, whatever.” He rolls his eyes, pulling his legs back, letting the swing twist back into place, looking back up at the stars. “Just know I’m gonna be the best setter in the world, and you’re gonna be pissed you gave up the sport, never to spike one of my sets again.” 

“I’ll be more than happy with my own future. I’m gonna own a restaurant one day, you’ll be begging for my cookin’ every night.”

“We’ll see about that.” Atsumu doesn’t look away from the stars.

Osamu has always been his drive, his direct competition, their rivalry has fueled them both throughout their entire lives, never faltering. They’ve done everything together, and turned it into a competition, it’s how they kept going. 

This isn’t the first time they’re on their own for something, the first time they were forced apart was when Osamu presented as an Alpha. Only they couldn’t control that, Osamu didn’t purposely present differently than his brother. This, quitting volleyball, taking his life in a different direction, this is his own choice. 

Osamu grabs the chain of Atsumu’s swing, pulling him back over, forcing his brother to look at him. “I mean it, I’ll make a name for myself, I’ll open a restaurant with the best damn Onigiri you’ve ever had! I’ll be happier than you’ll ever be.”

Atsumu lunges forward, grabbing the chain’s of Osamu’s swing, pulling on them, “Like hell! I’ll live a happier life, just you see!”

Osamu tugs hard on the chain, Atsumu flying off his swing, landing on his ass. Osamu barks out a laugh, only for his brother to grab his legs, pulling him off his own swing, his back hits the ground with a thud. 

Atsumu scrambles up and tries to make a break for the door. Osamu recovers quickly, jumping off the ground and onto his brothers back, the two of them crashing to the grass, Osamu gains control quickly, pinning his brother to the ground with a laugh.

Atsumu pushes at his face, but there’s no cruel intent behind it, the grin plastered across his face speaks for itself. 

They’re gonna be okay.

**Author's Note:**

> Comment and Kudos please!! I'd love to know what u guys thought!!
> 
> I have an idea for a post timeskip SakuAtsu that fits in this au so i hope i can get around to writing that, and that you guys stick around to read it!
> 
> come talk to me on [tumblr](http://mintberries.tumblr.com/) or [twitter](https://twitter.com/mintberries1) ! send an ask/dm i would love to talk about haikyuu!!


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